I believe that GNUstep has the best API of any of the available options for Linux/BSD app development. I also believe that if a GNUstep based desktop environment looked as good, and worked as well, as Mac OS X did in its heyday, we would get a lot more love from the programmers out there who are sick of GNOME and KDE's crap.

Maybe even enough interest to find someone willing and able to make Swift or Go or Rust first-class bindings to GNUstep. I like Objective-C, but more languages is the opposite of a problem.